1. Field of the Invention
The present invention relates to a liquid repellent member, a method for manufacturing such a liquid repellent member, an ink jet head using such a liquid repellent member, a method for manufacturing such an ink jet head, and a method for supplying ink.
2. Description of the Related Art
In the past, a liquid repellent member having a surface for increasing a contact angle with respect to liquid has been used as various applications for various purposes. For example, the liquid repellent member is used in an ink jet head. In some ink jet heads, a discharge port constituting member for defining a plurality of discharge ports for discharging ink has a discharge port surface in which the plurality of discharge ports are formed, and such a discharge port surface is constituted by a liquid repellent member having liquid repellency.
Conventionally, as disclosed in U.S. Pat. Nos. 4,694,308, 4,716,423, 5,262,802 and 5,300,959, the discharge port constituting member of the ink jet head has been formed from nickel, polysulfone resin or polyimide resin. Further, in some examples, such a member is formed from a metal plate such as stainless steel, rather than nickel.
In order to achieve the liquid repellency of the discharge port surface of the discharge port constituting member, for example, when the discharge port constituting member is formed from polysulfone resin or polyimide resin, the repellency is realized by coating fluoride on the discharge port surface or by performing fluorine-plasma treatment. However, when the fluoride is coated, the fluoride is easily peeled by stress in a wiping operation, and, when the fluorine-plasma treatment is used, since the fluoride is merely formed as a surface layer of the discharge port surface having a thickness of about several xc3x85, the fluoride is lost by wear due to stress in the wiping operation or the entire surface of the discharge port surface is not covered by the fluoride to create a surface portion having no fluoride, with the result that adequate liquid repellency cannot be obtained.
For example, Japanese Patent Application Laid-open No. 05-116325 (1993) discloses a method (fluorine-plasma treatment) for forming a liquid repellent film having Fxe2x80x94C bonding by forming a carbon skin film by deposition and by effecting discharging of the carbon skin film under the presence of nitrogen fluoride compound to generate plasma including fluorine.
According to this method, it is merely taught that a condition of the liquid repellent film has Fxe2x80x94C bonding. Further, a liquid repellent level of the liquid repellent film is evaluated to be similar to a liquid repellent level obtained when the fluorine-plasma treatment is effected with respect to carbon included in organic resin itself such as polysulfone. This means that the entire surface of the liquid repellent film is not always in the Fxe2x80x94C bonding condition.
Now, the reason will be explained.
When a carbon film is formed on a substrate 21 as shown in FIG. 25A by deposition, gloss of a surface of the substrate 21 is being lost. The reason is that, when fine carbon particles 22 are adhered to a film forming surface under the vacuum, since deposit as shown in FIG. 25B is formed, the surface becomes unevenness microscopically.
Thus, although it looks like that an Fxe2x80x94C film is formed through the entire surface, as shown in FIG. 25C, microscopically, since the fluorine-plasma is not adhered to bottoms 24 of recesses and shadow areas of the fine carbon particles 22, the Fxe2x80x94C film 23 is hard to be formed through the entire surface, and, in many cases, the entire Fxe2x80x94C film is not formed.
Thus, by the method for effecting the fluorine-plasma treatment with respect to the carbon deposit film, an ink repellent film having ink repellency similar to that in the method for for effecting the fluorine-plasma treatment with respect to the polysulfone resin is merely obtained. That is to say, in the obtained article, areas 24 having no ink repellent film are dotted on the discharge port surface (FIG. 26).
When clear ink (composition: PEG=15%, IPA=3%, water=82%) is discharged, it was found that the surface of the substrate having the ink repellent film formed in this way ensures adequate ink repellency even when wiping operations are repeated by 2000 times, but, when the wiping operations repeated by 3000 times, the ink repellency of the surface is reduced to decrease a contact angle to about 70xc2x0. In such a contact angle, good ink discharging cannot be achieved, thereby causing deviation and/or image unevenness.
Further, when an orifice plate is formed from stainless steel or nickel, water repelling particles such as fine Teflon particles are included by about 7% to 18% by plating or seizure to obtain the liquid repellency of the discharge port surface. However, since the size of the particle is greater than 0.01 xcexcm and the particles are not dispersed uniformly, in some cases, the discharging direction may become unstable. In this way, in the conventional orifice plates, adequate liquid repellency and endurance of liquid repellency cannot be obtained.
Further, coefficient of thermal expansion of metal used as material of the orifice plate is about 12 to 20xc3x9710xe2x88x926, and coefficient of thermal expansion of resin is about 8 to 200xc3x9710xe2x88x926. However, regarding the resins having the coefficient of thermal expansion of about 8 to 12xc3x9710xe2x88x926, in almost all cases, anisotropy is given by drawing/extending treatment so that the resin represents coefficient of thermal expansion of 8 to 12xc3x9710xe2x88x926 in a lateral direction (certain given direction) and coefficient of thermal expansion of about 50 to 100xc3x9710xe2x88x926 in a longitudinal direction (direction perpendicular to the certain given direction). Alternatively, a large amount of lithium oxide or ceramic filler representing negative coefficient of thermal expansion may be added to the resin.
In a case where the orifice plate is formed from a plate made of resin including such mix filler, when the discharge ports are formed in the orifice plate, shapes of the discharge ports will be distorted. In this case, when a diameter of the discharge port is about 60 xcexcm, since the mix filler affects little influence upon the shapes of the discharge ports, the ink is discharged without any problem, but, when the diameter of the discharge port is smaller than about 15 xcexcm, since the mix filler affects great influence upon the shapes of the discharge ports, the shapes of the discharge ports are greatly deformed, with the result that a stable image can almost not be obtained.
On the other hand, a plurality of recording elements provided in correspondence to the plurality of discharge ports to apply energy for discharging the ink to the ink are constituted by heat generating elements or piezo-vibration elements, and these elements are provided on a substrate made of silicon or ceramic. Coefficient of thermal expansion of the substrate is about 3 to 6xc3x9710xe2x88x926/xc2x0 C. Since such an ink jet head is driven to perform discharging operations by about 10000 times per second, a temperature of the head reaches about 70 to 80xc2x0 C.
In such a condition, when a length of the ink jet head exceeds 0.85 inch (about 20 mm), the following problems will arise.
In a case where difference in coefficient of thermal expansion is greater than 4xc3x9710xe2x88x926, if difference in temperature becomes about 60xc2x0 C. (for example, the temperature of the head is changed from 20xc2x0 C. to 80xc2x0 C.), a relative position between the driving element and the discharge port will be changed by 4 xcexcm or more.
If the difference is 4 xcexcm, when the ink is discharged onto the entire surface of a recording medium by serial print, positional deviation of 4 xcexcm is generated in every scan, thereby causing density unevenness.
Accordingly, in an ink jet head in which a length of the ink jet discharging element substrate is selected to 20 mm or more in consideration of the influence of the difference in coefficient of thermal expansion between the ink jet discharging element substrate and the orifice plate, the temperature of the head is detected, and, when the temperature change reaches 30 to 40xc2x0 C., the driving of the head is temporarily stopped, and, after the head temperature is decreased, the print is re-started. Particularly, when photo-like image print is effected, further careful head driving is required.
In this way, when a length of discharge port array is increased or arranging density of the discharge ports is increased in order to achieve higher speed and highly fine recording, the positional relationship between the orifice plate and the discharge element substrate is deviated due to the difference in coefficient of thermal expansion, abnormal ink flying may be generated in the vicinity of both ends of the discharge elements or the head may be damaged.
As mentioned above, the characteristics required for the discharge port constituting member (orifice plate) are that the discharge port surface has high ink repellency and the endurance of the ink repellency is excellent and that the coefficient of thermal expansion of the substrate (discharge element substrate) on which the discharge elements are provided is substantially the same as that of the orifice plate. However, as mentioned above, the conventional discharge port constituting members cannot satisfy these characteristics.
Accordingly, an object of the present invention is to provide an ink jet head and a method for manufacturing such an ink jet head, in which stable and high quality recording can be achieved by adopting a discharge port constituting member using a liquid repellent member satisfying the above characteristics.
The present invention achieves the above object by providing a liquid repellent member, a method for manufacturing such a liquid repellent member, an ink jet head using such a liquid repellent member, or a method for manufacturing such an ink jet head according to the following aspects (1) to (30).
(1) A liquid repellent member applied to ink jet, comprising a carbon substrate, and a liquid repellent film formed on a surface of the carbon substrate and formed by bonding between carbon and fluorine.
(2) A liquid repellent member applied to ink jet, comprising an FC ink repellent film formed by forming a through-hole in a carbon substrate and by electrolytically processing the substrate in molten salt of fluoride.
(3) A method for manufacturing a liquid repellent member which comprises a carbon substrate and on a surface of which a liquid repellent film formed by bonding between carbon and fluorine is formed, comprising a step for forming the liquid repellent film on the surface.
(4) A method according to the aspect (3), further comprising a step for forming the liquid repellent film on the surface by applying voltage to the carbon substrate in a condition that the carbon substrate is immersed in molten salt of fluoride.
(5) A method according to the aspect (3), further comprising a step for forming the through-hole by illuminating femtosecond laser onto the liquid repellent member.
(6) A method according to the aspect (5), wherein the step for forming the through-holes is effected while sending out gas including oxygen in the vicinity of an area of the liquid repellent member on which the femtosecond laser is illuminated.
(7) A method for manufacturing a plurality of liquid repellent members on surfaces of which liquid repellent films formed by bonding carbon and fluorine are formed, comprising the steps of collectively forming the liquid repellent films on the surfaces of the carbon plate by applying voltage to the carbon plates in a condition that a carbon plate corresponding to the plural liquid repellent members is immersed in molten salt of fluoride, and dividing the carbon plate formed with the liquid repellent films to obtain the plural liquid repellent members.
(8) An ink jet head comprising a discharge port constituting member formed from carbon and having a plurality of discharge ports for discharging ink, and a discharge port surface on which an ink repellent film formed by bonding between carbon and fluorine is provided.
(9) An ink jet head according to the aspect (8), further comprising a silicon recording element substrate on which a plurality of recording elements for applying energy for discharging ink from the respective discharge ports to the ink are provided in correspondence to the plurality of discharge ports.
(10) An ink jet head according to the aspect (8), wherein the discharge port constituting member comprises crystal body or non-crystal body of carbon.
(11) An ink jet head according to the aspect (10), wherein the crystal body is single crystal body.
(12) An ink jet head according to the aspect (10), wherein the non-crystal body is carbon compound including nitrogen.
(13) An ink jet head according to the aspect (10), wherein the discharge port constituting member has ink flow paths communicated with the respective plural discharge ports.
(14) An ink jet head according to the aspect (13), wherein the discharge port constituting member has a common ink flow path with which the plurality of ink flow paths are communicated.
(15) An ink jet head according to the aspect (8), wherein the discharge port constituting member has a rib on a side of the discharge port surface.
(16) A method for manufacturing an ink jet head comprising a discharge port constituting member formed from carbon and having a plurality of discharge ports for discharging ink, and a discharge port surface on which an ink repellent film formed by bonding between carbon and fluorine is provided, comprising a step of forming a discharge port constituting member, said step including a step of forming said ink repellent film on said discharge port surface and a step for forming said plurality of discharge ports on said constituting member formed with said ink repellent film.
(17) A method according to the aspect (16), wherein the processing for forming the discharge port constituting member includes a step for forming the liquid repellent film on the discharge port surface by applying voltage to the discharge port constituting member in a condition that the discharge port constituting member is immersed in molten salt of fluoride.
(18) A method according to the aspect (17), wherein the processing for forming the discharge port constituting member includes a step for polishing a surface of the discharge port surface of the discharge port constituting member to a flat state, and a step for forming the liquid repellent film on the discharge port surface by applying the voltage to the discharge port constituting member in a condition that the polished surface of the discharge port constituting member is immersed in the molten salt of fluoride.
(19) A method according to the aspect (18), wherein, in the processing for forming the discharge port constituting member, the polishing step is a step for effecting the polishing while fixing a surface opposite to the surface of the discharge port surface of the discharge port constituting member onto a polishing table, and the step for forming the ink repellent film is effected in a condition that the discharge port constituting member is fixed to the polishing table.
(20) A method according to the aspect (17), wherein a step of forming said discharge port constituting members comprising a step for collectively forming the ink repellent films on the discharge port surfaces of a plurality of discharge port constituting members by applying voltage to a carbon plate in a condition that the carbon plate corresponding to the plurality of discharge port constituting members is immersed in the molten salt, and a step for dividing said carbon plate formed with said ink repellent film into said plurality of discharge port constituting members.
(21) A method according to the aspect (20), wherein the processing for forming the discharge port constituting member includes a step for polishing a discharge port surface side surface of the carbon plate to a flat state, and a step for forming the ink repellent films on the discharge port surfaces by applying voltage to the discharge port constituting members in a condition that the polished surfaces of the discharge port constituting members are immersed in the molten salt of fluoride.
(22) A method according to the aspect (21), wherein, in the processing for forming the discharge port constituting member, the polishing step is a step for effecting the polishing while fixing a surface of the carbon plate opposite to the discharge port surface side surface onto a polishing table, and the step for forming the ink repellent films is effected in a condition that the carbon plate is fixed to the polishing table.
(23) A method according to the aspect (16), wherein the processing for forming the discharge port constituting member includes a step for forming the plurality of discharge ports by illuminating femtosecond laser onto portions corresponding to the plurality of discharge ports of the discharge port constituting member.
(24) A method according to the aspect (23), wherein the step for forming the discharge ports is effected while sending out convey gas having oxygen density of 5 to 10% onto an area in the vicinity of a portion of the discharge port constituting member onto which the femtosecond laser is illuminated.
(25) A method for supplying ink to an ink jet head, wherein the ink jet head comprises a liquid repellent member having an FC ink repellent film formed by forming a through-hole in a carbon substrate and by electrolytically processing the substrate in molten salt of fluoride, an air suction hole, ink, an ink jet discharge element, an ink absorbing body, an ink jet head frame and an air suction device.
(26) A method according to the aspect (25), wherein the liquid repellent member and the ink absorbing body are arranged in contact with each other, and the ink is supplied to the ink jet head by sucking air from the air suction hole provided in the liquid repellent member.
(27) A method according to the aspect (26), wherein the air suction hole is located at a position different from a position of an ink supply port to the ink jet discharge element.
(28) A method according to the aspect (27), wherein suction pressure for the air is smaller than meniscus maintaining pressure of the ink jet discharge element.
(29) A method according to the aspect (28), wherein the supplying of the ink is effected by thrusting an ink supply needle to suck the air from the air suction hole.
(30) A method for manufacturing a liquid repellent member in which a liquid repellent film is formed on a surface of a substrate, comprising a step for forming the liquid repellent film on the surface of the substrate by applying voltage to the substrate in a condition that the substrate is immersed in molten salt of fluoride.
Incidentally, in the present invention, the carbon substrate includes a structure comprised of carbon compound including nitrogen of about several %, as well as a structure comprised of carbon atoms of 100%.